A full moon rises behind the ancient temple of Poseidon in cape Sounio, south of Athens. The complete lunar eclipse Friday when the sun, Earth and moon line up perfectly to cast Earth’s shadow on the moon, will be the longest this century. It’s called a “blood moon” because it turns a deep red and will be visible at different times around the world.(Thanassis Stavrakis / Associated Press)
The moon during the total lunar eclipse taken from the Israeli Mediterranean coastal city of Netanya.(JACK GUEZ / AFP/Getty Images)
People gather as they wait for the sun to go down and the appearance of the ‘Blood moon’ in Berlin.(TOBIAS SCHWARZ / AFP/Getty Images)
A blood moon rises over Tel Aviv, Israel.(Ariel Schalit / Associated Press)
People set up telescopes to witness a rare lunar eclipse near National Sun Yat-sen Memorial Hall in Taipei, Taiwan.(Billy H.C. Kwok / Getty Images)
People use binoculars to watch a rare lunar eclipse in Taipei, Taiwan.(Billy H.C. Kwok / Getty Images)
People set up telescopes to witness a lunar eclipse in Taipei, Taiwan.(Billy H.C. Kwok / Getty Images)
The full moon rises near Bondi Beach ahead of a total lunar eclipse in Sydney. The period of totality during this eclipse, when Earth’s shadow is directly across the moon and it is at its reddest, will last 1 hour, 42 minutes and 57 seconds, making it the longest viewable lunar eclipse this century.(Brook Mitchell / Getty Images)
The longest lunar eclipse of the 21st century is coming up, and you don’t want to miss it.
On Friday, the moon will be fully engulfed in the heart of Earth’s shadow for 1 hour, 42 minutes and 57 seconds.
It doesn’t get much better than that. The longest possible duration of a lunar eclipse is one hour and 47 minutes, according to EarthSky.org.
If you live in North America, you will not be able to see the marathon celestial event in person — unless you live in the far eastern part of Newfoundland. Unfortunately the event will be occurring during our daytime. But if you happen to be in eastern South America, Europe, Africa, the Middle East, Asia or Australia, you are in luck. The rest of us will just have to watch online.
Even though the Earth will be lined up directly between the moon and the sun, the moon will not be blacked out completely.
Instead, it will appear to be a deep copper red as it reflects the scattered light of all the sunsets and sunrises on Earth back at us.
If you were standing on the moon at the time of the eclipse, the Earth would look like a black disk outlined in glowing red. That’s because some light from the sun bends around the edge of the Earth where the blue and green wavelengths are scattered by our atmosphere.
There are a few reasons that Friday night’s eclipse will last so long.
Every time there is an eclipse, the moon passes through the Earth’s shadow, but it doesn’t always pass through the same part of the shadow.
As you would expect, the shadow of the Earth looks like a disk. Sometimes the moon passes through the top of the disk, or toward the bottom. During this week’s lunar eclipse, however, the moon will pass close to middle of the disk.
“The Moon is passing very close to the center of Earth’s shadow, so it is passing on a chord that almost equals the full diameter of the shadow,” said Steve Edberg, a recently retired astronomer at the Jet Propulsion Laboratory in La Cañada-Flintridge. “In other words, the moon is taking almost the longest possible path through Earth’s shadow.”
In addition, the Earth is farther from the Sun during the northern hemisphere summer, so its shadow is larger than average, he said.
And finally — the Moon is near apogee (the most distant point in its orbit) around the July full moon, Edberg said. So it is moving slower in its orbit and taking more time in the shadow.
Friday night’s lunar eclipse will be more than 20 minutes longer than the last one, which occurred earlier this year on Jan. 31. That one lasted for one hour and 16 minutes, according to NASA.
The next one, which is coming up on Jan. 21, 2019, will be 1 hour and 2 minutes.
The shortest eclipse of the century occurred just three years ago on April 4, 2015. It lasted for 4 minutes and 43 seconds.
Even if you can’t see Friday night’s eclipse in real life, you can watch it on your computer. The website timeanddate.com will be livestreaming the eclipse beginning at 11 a.m. PDT Friday. The partial eclipse will begin at 11:24 a.m. — that’s when the Earth’s shadow will begin to creep across the moon. The full eclipse starts at 12:30 p.m. PDT and ends at 2:13.
If you don’t want to tune in for the whole show, I suggest watching just before 12:30. That way you can see the moon move full into the Earth’s shadow. It will give you a sense of the clockwork of our solar system.
And last but not least: Mars just happens to be in opposition on Friday night as well. That means it will be shining extra-bright in the night’s sky.
A red planet glowing next to a red moon — it should be a beautiful show.
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